This invention relates in general to electromagnetically actuated friction clutch assemblies and in particular to an improved structure for a combined coil housing and shaft bearing for use in such an electromagnetic friction clutch assembly.
Electromagnetic friction clutch assemblies are well known devices which are commonly used to selectively connect a rotatably driven input member with an output member. The input member of a typical electromagnetic friction clutch assembly is usually embodied as an input gear, which meshes with and is constantly rotatably driven by a source of rotational power. The output member is usually embodied as a cylindrical shaft. The input gear is usually supported on the output shaft for rotation relative thereto. An armature, also rotatably supported on the output shaft, is connected to the input gear for rotation therewith and for relative axial movement. A rotor is secured to the output shaft for rotation therewith. The armature is axially movable between engaged and disengaged positions. In the engaged position, the armature frictionally engages the rotor so as to cause the output shaft to be rotatably driven by the input gear. In the disengaged position, the armature does not frictionally engage the rotor, and the output shaft is not rotatably driven by the input gear. A non-rotatable electromagnet is supported on the rotor for selectively attracting the armature toward the rotor so as to engage the electromagnetic friction clutch assembly such that the output shaft is rotatably driven by the input gear.
As noted above, the input gear and the output shaft of a conventional electromagnetic friction clutch assembly must be able to accommodate relative rotational movement. Also, the non-rotatable electromagnet must be supported on the rotatable rotor to accommodate relative rotational movement. Thus, it is known to provide conventional bearings in the electromagnetic friction clutch assembly for these purposes. Typically, the input gear of the electromagnetic friction clutch assembly is supported on the output shaft by a plurality of needle bearings, while the electromagnet is supported on the rotor by a sleeve bearing formed from a relatively low friction material. Additionally, a thrust bearing may be provided between the input gear and the rotor to accommodate axial forces which may be generated during operation.
While such mechanical bearings have been found to function satisfactorily, their presence requires that they occupy physical space within the electromagnetic friction clutch assembly. This results in a decrease in the amount of physical space which could be used by the other components of the electromagnetic friction clutch assembly to increase the torque capacity thereof. Also, the presence of these bearings can interfere with the magnetic field generated by the electromagnet when energized, thus also reducing the torque capacity of the electromagnetic friction clutch assembly. Accordingly, it would be desirable to provide an improved structure for an electromagnetic friction clutch assembly which does not require the use of mechanical bearings.